[dvipdfmx] dvipdfmx: wrong exit status

[Karl Berry]

Hi Shunsaku,

    I think this is the same behavior as dvipdfm and also as dvips.

Huh. I didn't realize. Well, the behavior when acting as dvipdfm
shouldn't be changed, but I think I'll try to change dvips. I see no
reason why a missing image shouldn't be an error there as well.

    I don't know why but there must be a reason for choosing
    such behavior.

I don't think so. Just random. "I can still generate an output file, so
let's output successfully." No ...

    If there are not so many practical benefits I'd rather choose
    leaving this unchanged.

The reason I think (x)dvipdfmx is the most important place to exit with
bad status when an image isn't found is because of its function as the
backend for xetex. If XeTeX found the image and xdvipdfmx didn't,
something is badly awry with the user's search paths (or something), and
they wouldn't necessarily realize this unless they actually looked at
the output page.

Wdyt? --thanks, karl.